Development of Aromatic Amino Acid Hydroxylases as Therapeutics The long-term goal of the research is to develop mammalian aromatic amino acid hydroxylases as therapeutics in the treatment of metabolic disorders such as Parkinson's disease (tyrosine (tyrosine hydroxylase), Segawa's syndrome (tyrosine hydroxylase) and phenylketonuria (phenylalanine hydroxylase). The research design is to develop a high throughput screen that will detect mutant hydroxylases with increased activity and/or stability. The mutant enzymes that possess the desired characteristics of increased activity and/or stability will be targeted as candidates for gene therapy in the treatment of Parkinson's, Segawa's syndrome and phenylketonuria. The high-throughput screen will be based on a co-expression system that produces the hydroxylase and a second enzyme that converts the product of the hydroxylase into a colored compound that can be easily detected and assay. The proposed research provides the first step in achieving the long-term goal, because it supports the development of co-expression systems that will serve as the starting material for the mutagenesis and screening process.